Electric engine-starting motors



April 960 A. H. SEILLY 2,934,656

ELECTRIC ENGINE-STARTING MOTORS Filed Feb. 19, 1957 2 SheetsSheet l .Znuemv flJ izsel/l April 26, 1960 A. H. SEILLY ELECTRIC ENGINE-STARTING MOTORS 2 Sheets-Sheet 2 Filed Feb. 19, 1957 United tates Patent 2,934,656 ELECTRIC ENGINE-STARTING MOTORS Alec Harry Seilly, North Wembley, England, assignor to C.A.V. Limited, London, England Application February 19, 1957, Serial No. 641,117

Claims priority, application Great Britain February 20, 1956 1 Claim. (Cl. 290-38) This invention relates to electric engine-starting motors of the kind in which motion is transmitted from the motor to the engine by a pinion axially engageable with a toothed wheel on the engine and having a quick-pitch screw or equivalent connection with a shaft driven by the motor armature, the engagement of the pinion with the engine wheel being effected by the interaction of the pinion and shaft when the motor is set in motion.

A well known trouble associated with a starting motor of the kind aforesaid is that, as a consequence of wear or other injury to the teeth of the pinion or wheel, jamming is liable to occur when the pinion encounters the wheel, and in an extreme case, it may be necessary to dismantle the motor before release can be effected.

The object of the present invention is to provide a construction whereby disengagement of a jammed pinion from the engine wheel can be effected automatically.

A starting motor embodying the invention includes an armature driven shaft having a limited axial freedom of movement, and an adequately strong spring means which is compressed by axial movement of the shaft when the pinion encounters the wheel on the engine, the arrangement being such that in the event of jamming and on re-opening the motor controlling switch the spring means imparts an opposite axial movement to the shaft so causing a sufficient reverse movement to be given to the pinion to effect its release.

In the accompanying drawings, Figure 1 is a part sectional side elevation of an engine-starting motor of the kind specified and provided with one form of the invention.

Figures 2 and 3 are detail views exemplifying alternative means for use in a motor as shown in Figure 1.

Referring to Figure 1, the construction of the pinion a and its driving shaft b may be of any convenient known form, the pinion having a quick-pitch screw thread connection with the shaft and being loaded by a spring 0 which normally serves to assist return of the pinion to its inactive position after the engine has been started.

According to the invention the shaft b which is driven by and extends through the armature d, is provided with a small amount of axial freedom, about inch being usually sufiicient, and the bearing e at the end of the motor housing remote from the pinion a is shaped to form an abutment 1 which by co-operation with a shoulder g on the commutator h of the armature serves to determine the extent of this axial freedom. Also there is provided an adequately strong spring means acting in the direction for moving the armature away from the bearing.

The spring means may be provided in any of a variety "ice of forms. In the example shown in Figure 1, a helically coiled spring i is located in a bore in one end of the shaft b, with one end supported by a cap 1' attached to the said bearing, the cap and spring being provided with abutment pieces k between which is contained a thrust ball m. Alternatively a helically coiled spring i may be arranged betwen the end of the shaft b and the cap as shown in Figure 2. In another arrangement one or more Belleville washers n, that is, dished resilient washers, are placed between the shoulder on the commutator and the abutment on the adjacent hearing as shown in Figure 3.

The arrangement is such that in the event of jamming of the pinion when it encounters the engine wheel, the spring means above described is compressed. On reopening the motor switch, the energised spring means then imparts an axial movement to the shaft relatively to the stalled pinion, so imparting an angular movement to the pinion in the direction for releasing it from the engine wheel. Thereupon the spring 0 associated with the pinion imparts to it an axial movement for disengaging it from the engine wheel. On re-closing the switch the pinion is again moved into engagement with the wheel, and this time or after successive trials the pinion may engage the wheel properly.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

An electric starting motor for an internal combustion engine having thereon a toothed wheel through the medium of which the engine can be started by the motor, comprising in combination with the motor armature, a shaft which extends coaxially through and is constructed and arranged to be driven by the motor armature, a pinion which is mounted on and has a helical connection with one end portion of the shaft,.and which is movable axially on the shaft, into a position for engaging the toothed wheel on the engine, under the action of the helical connection when the shaft is rotated as a result of the motor being set in motion, spring means which is arranged to act on the opposite end portion of the shaft for normally preventing the latter from moving axially in the direction opposite to the wheel-engaging movement of the pinion, but against the action of which the shaft is movable axially to a limited extent in the event of the wheel-engaging movement of the pinion being prematurely terminated by contact of the pinion with the wheel, so that in the event of jamming of the pinion against the wheel the spring means can serve, when rotational movement of the shaft is interrupted by the de-energization of the motor, to impart an opposite axial movement to the shaft, and thereby cause sufficient reverse rotational movement of the pinion to effect its release from the wheel.

References Cited in the file of this patent UNITED STATES PATENTS r 1,215,453 Wilson Feb. 13, 1917 1,341,659 Millward June 1, 1920 1,440,697 Richards Jan. 2, 1923 1,563,992 Huntley Dec. 1, 1925 2,151,492 Weiss Mar. 21, 1939 FOREIGN PATENTS 17,008 Great Britain of 1915 

